I just bought a house that has a Clayton 1800 wood burner with a blower. It is duct into the existing furnace already and has been used in the past. Wiring is disconnected and I can figure that out. What I dont know is the thermostat is disconnected from the back of the unit. What is its function as far as the fan function, unit has a manual switch for a 3 speed fan, and regulating heat? How do I connect the thermostat that is disconnected? Should I upgrade this thermostat? Why are there two thermostats? Any help would be great.